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Determine the best method to solve the system of equations. Then solve the system.

5x+7y=-11

5x-3y=19

Guest Mar 6, 2017

Best Answer 

 #1
avatar+4161 
+6

The fastest method looks like "elimination," where you line the equations up and add straight down.

5x + 7y = -11

5x - 3y = 19

If we added straight down right now, that would give us 10x + 4y = 8, which doesn't help any. We want one of the variables to go away.

 

Multiply the top equation by negative one all the way through.

(-1)(5x + 7y) = (-1)(-11)

-5x - 7y = 11

 

Now line up both equations and add straight down:

-5x - 7y = 11

5x - 3y = 19    

0 - 10y = 30

 

-10y = 30

y = -3

 

Plug in y into either one of the equations to find x:

5x - 3(-3) = 19

5x + 9 = 19

5x = 10

x = 2

hectictar  Mar 6, 2017
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1+0 Answers

 #1
avatar+4161 
+6
Best Answer

The fastest method looks like "elimination," where you line the equations up and add straight down.

5x + 7y = -11

5x - 3y = 19

If we added straight down right now, that would give us 10x + 4y = 8, which doesn't help any. We want one of the variables to go away.

 

Multiply the top equation by negative one all the way through.

(-1)(5x + 7y) = (-1)(-11)

-5x - 7y = 11

 

Now line up both equations and add straight down:

-5x - 7y = 11

5x - 3y = 19    

0 - 10y = 30

 

-10y = 30

y = -3

 

Plug in y into either one of the equations to find x:

5x - 3(-3) = 19

5x + 9 = 19

5x = 10

x = 2

hectictar  Mar 6, 2017

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